Mold for use in the manufacture of optical elements



Sept. 3, 1

946 D. P. I COOPER, JR 4 MOLD FOR USE IN THE MANUFACTURE OF OPTICAL ELEMENTS Filed Sept. 2, 1942- Patented Sept, 3, i946 2,406,742 MOLD FOR USEZIN THE MANUFACTURE OPTICAL ELEMENTS V Dexter P. Cooper, Jr., Cambridge, Mass, assignor to Polaroid Corporation, Cambridge, Mass, a corporation of Delaware Application September 2, 1942, Serial No. 457,032

13 Claims.

This invention relates to an improved mold for use in the manufacture of optical elements formed of polymerized synthetic plastics, resins and like materials.

An object of the invention is to provide a mold of the character described comprising a plurality of elements having optically smooth molding surfaces and a relatively low melting-point cement for sealing the joints between said molding elements and holding them fixedly in position during the molding process. 1

Another object of the invention is the provision of a fusible cement which remains hard at temperatures at which the polymerization process faces, which can be repeatedly re-used, and these elements should preferably be bonded together and maintained in proper position by an adhesive or a cement which may be readily applied, easily removed, and which will stand the temperatures to which the molds are subjected during the polymerization of the plastic material therein. With plastic materials of the class heretofore described polymerization temperatures are preferably maintained not greatly in excess of 90 degrees C.

This invention contemplates the use of a fusible V cement, and preferably one having a relatively low melting point as the material employed in sealing and bonding together the mold walls. The mold takes place 5 may be assembled by placing the glass wall ele- Other objects of the invention will in part merits in a suitable jig, and while'they are held be obvious and will in part appear hereinafter. position in the j g, or ex p y leaf p g The invention accordingly comprises the prodother means, y e Sealed along e r a jeuct possessing the features, properties, and rela- Cent edges a Cemented t e y pp y tion of elements which will be exemplified in the thereto the preferred es e or ce ent in 11101- following detailed disclosure and the scope of the ten condition The Cement y then be Cooled application of which will be indicated in the a it q y sets and hardens. claims, The drawing illustrates in perspective a portion For a fuller understanding of the invention ML of a mold for s i th an a t of p sms. erence should be had to the following detailed de- The mold walls ill are shown as made of gla scription taken in connection with the accomthe pre material, and y a bonded opanying drawing, which represents partially in gether and held in position by the fusible cement perspective and partially in sectioncone embodi- A bottom Plate '4 i also held in position by ment of the invention. the cement l2.

There is today a pressing demand for large A pr err m t rial fo se as the b n n quantities of optical elements, such as prisms, material in the present invention is a relatively lenses and the like. This invention is concerned 0W m n -P y, Such as the alloy known with the provision of molds adapted for use in the as S ta or the alloy known as Roses production of such elements from synthetic plasetal. Any other fusible cement may e e tic or resinous materials which are introduced p y d v d it s s at a t p atur above, into the mold in a partially polymerized or monob t n t r y above, t t mp p y meric state and then polymerized substantially in effecting substantial polymerization of the completely and until they form hard, transparent molded plastic. A fusible cement having a meltoptical elements. Materials which have been ing p i n r tly'in excess of 90 de s C- found particularly useful in the production of 4,0 is p fe red- Slleh a c ent y be p d such molded plastic optical elements are cycloaround the mold jo ts Without j y o t e hexyl methacrylate, styrene, methyl methacrylate glass mold walls and it may be readily removed and imila materi ls, from the mold, melted and re-used, the removal A considerable percentage of the cost of the being accomplished at a temperature which does molded optical element resides in the cost of the o injure the molded plastic. mold. The light-transmitting surfaces of the ele- Since certain changes may be made in the above ment are preferably molded in contact with glass p d t and different embodiments of the invenelements having optically smooth surfaces, and tion could be made without departing from its these are expensive. It will be apparent that in scope, it is intended that all matter contained in the production of large quantities of molded opthe above description or shown in the accompanytical elements it is highly desirable that the mold ing drawing shall be interpreted as illustrative may be readily and rapidly assembled and that it and not in a limiting sense.

should be easily removed from the finished ar- It i also to be understood that the following ticle. It should comprise elements, and particuclaims are intended to cover all the generic and larly those elements having optically smooth surspecific features of the invention herein described,

3 and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed is:

1. A mold for use in the formation of an optical element of polymerized synthetic plastic material or the like, comprising, in combination, a plurality of mold Walls having molding surfaces substantially optically smooth, and a cement bonding said walls together and comprising Woods metal.

2. A mold for use in the formation of an optical element of polymerized synthetic plastic material or the like, comprising, in combination, a plurality of mold walls having molding surfaces substantially optically smooth, anda cement bonding said walls together and comprising Roses metal.

3. A mold for use in the formation of an optical element of polymerized synthetic plastic material or the like, comprising, in combination, a plurality of mold walls having molding surfaces substantially opticallysmooth and defining the outer surfaces of the mold cavity, and a cement bonding said'walls together and comprising an alloy havinga melting point not greatly in excess of 90 degrees 'C.

'4. A mold'foruse in the formation of an optical element of polymerized synthetic plastic material orthe like, comprising, in combination, a plurality of substantially fiat, glass mold Walls having molding surfaces substantially optically smooth, anda cement bonding said walls together and comprising'an alloy having a melting point not greatly in excess of '90, degrees C.

'5. A mold for use in the formation of an optical element of polymerized synthetic plastic material or the .like which formation is effected at a temperature not exceeding apredetermined temperature, said mold comprising, in combination, a plurality of substantially flat, glass mold walls having molding surfaces substantially optically smooth, and a fusible, cement bonding sadi Walls'together, said cement having a melting point not greatly in excess of said predeterminedtemperature.

6. A mold for use in the formation of an optical element of polymerized synthetic plastic material orithe like which formation is effected at 'a temperature not exceeding a predetermined temperature, said mold comprising, in combination, a plurality of mold walls having molding surfaces substantially optically smooth and defining the outer surfaces of the mold cavity, and a fusible cement bonding said walls together, said cement having a melting point not greatly in excess of said predetermined temperature.

'7. A mold for use in the formation of an op- 'tical element of polymerized synthetic plastic or the like, comprising, in combination, a plurality of glass mold walls havingmolding surfaces sub- 4 stantially optically smooth, and a cement bonding said walls together and comprising Woods metal.

8. A mold for use in the formation of an optical element of polymerized synthetic plastic material or the like, comprising, in combination, a plurality of glass mold Walls having molding surfaces substantially optically smooth, and a cement bondin said walls together and comprising Roses metal.

9. A mold for use in the formation of an op tical prism of polymerized synthetic plastic ma& terial or the like, comprising, in combination, a plurality of substantially fiat glass mold walls having molding surfaces substantially optically smooth and forming a prismatic molding cavity, and a cement bonding said walls together and comprising Woods' metal.

1c. A mold for use in the formation of an optical prism of polymerized synthetic plastic material or the like, comp-rising, in combination, a plurality of substantially fiat glass-mold walls having molding surfaces substantially optically smooth and forming a prismatic molding cavity, and a cement bonding said Walls together and comprising Roses metal.

11. A mold for use in th formation of an optical element of polymerized synthetic plastic or the like, which formation is effected at a temperature not exceeding a predetermined temperature, said mold comprising a plurality of mold members, at least one of said members being formed of glass and having an optically smooth surface adapted to define a light-transmitting surface of said element, and a fusible cement bonding said members together, said cement having a melting pointnot greatly in excess of said predetermined temperature.

12. A mold for use in the formation of an optical element of polymerized synthetic plastic material or the like, comprising, in combination, a plurality of mold members, at least one of said members being formed of glass and having an optically smooth surface adapted to define a light-transmitting surface of said element, and a cement bondin said members together and comprising a metallic alloy havinga melting point not greatly in excess of 90 C.

13. A mold for use in the formation of an optical element of polymerized synthetic plastic material or the like, comprising, in combination, a plurality of glass mold walls having molding surfaces substantially opticall smooth and defining a prismatic molding cavity, and a cement bonding said walls together and comprising a metallic alloy having a melting pointnot greatly in excess of 90 C.

DEXTER P. COOPER, JR. 

